Fluvial response to abrupt global warming at the Palaeocene/Eocene boundary

• Published in: Nature (London) Vol. 491; no. 7422; pp. 92 - 95
• Main Authors: Foreman, Brady Z., Heller, Paul L., Clementz, Mark T.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.11.2012; Nature Publishing Group
• Subjects: 704/2151/213; 704/2151/413; Age; Altitude; Aluminum Silicates - analysis; Anthropogenic factors; Carbon dioxide; Carbon Dioxide - analysis; Carbon Isotopes; Cenozoic; Climate change; Colleges & universities; Colorado; Earth sciences; Earth, ocean, space; Environmental aspects; Eocene; Exact sciences and technology; Geochemical exploration, methodology, general; Geologic Sediments - analysis; Geomorphology; Global Warming; Greenhouse Effect; History, Ancient; Humanities and Social Sciences; Hypotheses; Lasers; letter; Levees & battures; Metallic and non-metallic deposits; multidisciplinary; Natural history; Oceans; Paleocene; Plants; Precipitation; Rain; Rivers; Sand & gravel; Sandstone; Science; Sedimentary basins; Sedimentary structures; Sediments; Sediments (Geology); Stratigraphy; Temperature; United States; Colorado; United States > US; Paleogene; stratigraphic boundary; Paleocene; North America; sandstone; paleoclimate; stratigraphy; greenhouse gas; lithofacies; paleoatmosphere; discharge; flux; Cenozoic; clastic rocks; climate change; sedimentary basins; carbon dioxide; stable isotopes; models; C-13/C-12; Tertiary; stratigraphic columns; deposition; Eocene; sedimentation; sedimentary rocks; sediment yield; global warming; sediment transport; channels; Phanerozoic; progradation; dimensions; streamflow
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature11513

The fluvial response in western Colorado to the Palaeocene/Eocene thermal maximum involves a large increase in sediment flux that lasted much longer than the vegetation, monsoon and carbon dioxide changes of the thermal maximum. A river's response to changing climate This study provides insights into the response of fluvial systems to climate change. A shift in the nature of fluvial deposits is found to coincide with the Palaeocene/Eocene thermal maximum, a prominent global-warming event that took place about 56 million years ago. The shift is interpreted as a sudden reorganization of river systems in western Colorado in response to profound changes in climate. The palaeo-landscape was slow to recover, with the change in runoff regime that is recorded in the fluvial patterns lasting long after the end of the warming event. Climate strongly affects the production of sediment from mountain catchments as well as its transport and deposition within adjacent sedimentary basins 1 , 2 , 3 . However, identifying climatic influences on basin stratigraphy is complicated by nonlinearities, feedback loops, lag times, buffering and convergence among processes within the sediment routeing system 3 , 4 . The Palaeocene/Eocene thermal maximum (PETM) arguably represents the most abrupt and dramatic instance of global warming in the Cenozoic era and has been proposed to be a geologic analogue for anthropogenic climate change 5 . Here we evaluate the fluvial response in western Colorado to the PETM. Concomitant with the carbon isotope excursion marking the PETM we document a basin-wide shift to thick, multistoried, sheets of sandstone characterized by variable channel dimensions, dominance of upper flow regime sedimentary structures, and prevalent crevasse splay deposits. This progradation of coarse-grained lithofacies matches model predictions for rapid increases in sediment flux and discharge 1 , 3 , instigated by regional vegetation overturn 5 , 6 and enhanced monsoon precipitation 7 , 8 . Yet the change in fluvial deposition persisted long after the approximately 200,000-year-long PETM 9 with its increased carbon dioxide levels in the atmosphere, emphasizing the strong role the protracted transmission of catchment responses to distant depositional systems has in constructing large-scale basin stratigraphy. Our results, combined with evidence for increased dissolved loads 10 and terrestrial clay export 5 , 11 , 12 to world oceans, indicate that the transient hyper-greenhouse climate of the PETM may represent a major geomorphic ‘system-clearing event’ 13 , involving a global mobilization of dissolved and solid sediment loads on Earth’s surface.